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    // 题目1(选做)：const arr=['name','age','hhh','hhh','age','hhh','hhh','hhh']各出现多少次
    // 要求输出一个对象如下：{age: 2,hhh: 5,name: 1}
    const arr = ['name', 'age', 'hhh', 'hhh', 'age', 'hhh', 'hhh', 'hhh']
    let obj ={}
    for (key of arr) obj[key] = obj[key]? obj[key]+1 : 1;
    
    // console.log(obj)

    // 题目2(必做)：现在两个数组，判断在a中的元素，不在b中 const a = [1,2,3,5] const b=[1,3,5,6] 将在a不在b中的筛选出来
    // 要求：输出一个数组：[2]
    const a = [1, 2, 3, 5]
    const b = [1, 3, 5, 6]
    const num = [];
    a.map( item => {
      const m = b.some(e => item ===e)
      if(!m) num.push(item);
      return num;
    })
    const c = []
    a.map(item =>{
      if(b.indexOf(item) === -1) c.push(item)
    })
    console.log(c)
    // const c =[]
    // const d =[]
    // a.map(item => item == b.map(q=>q)?d.push(item):c.push(item))
    // console.log(c)
    // console.log(num)
    // 题目3(必做):数组去重(可以用多种方法,至少写一种)
    // 要求：输出一个数组：[1,2,3,9]
    const arr2 = [1, 2, 3, 2, 9]
    // 方法1
    const arr3 =[]
    for(key of arr2){
      if(!arr3.includes(key))arr3.push(key)
    }
    console.log(arr3)
    


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